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Discussion Starter #1
I used the High Idle Procedure on as explained on this website http://www.gmupfitter.com/publicat/bull/bull53.pdf, I installed the PTO switch, had the mechanic at the dealer program it, but can't get it to work. Is it possible to do this on a 2500HD? Did anyone else ever try this???
 

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I believe that procedure is for cab & chassis truck's which I think are set up diffrent than our's.
I did the same PTO switch but I didn't need any dealer program.
There's one importnat part missing in that procedure which is, you still have to tap into the ECM with a 20 guage wire like the instruction's say else where on this site that explain's the high idle set up, and then instead of running the wire to the brake pedal like other's do you run the wire to a plug that's under the underhood fuse box. I don't remember exatly which one but the article should be around here somewhere.
And then it will work :)
 

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Discussion Starter #3
I tried searching for it, but I can't find it.:eek:
 

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Hmmmmm,
I can't log on there anymore

EDIT: Ok never mind I was able to log on.
And that is the instructions I used to do mine too

Thx for the write up, Spoolin it

So there you go wheatfield now you have all the instruction's on how to hook it up. The computer end takes a little time but is not hard and the other end at the connector is easy to do too
 

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Discussion Starter #7
Thank you guys, I'm gonna hook it up tonight. PS: the dealer had the terminals for the TCM in stock, it's a wonder, lol:)
 

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02 2500HD LB7
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No problem guys, now if GM had hooked us all up with an extra Censored $.02 worth of wiring none of would have to wire anything. :mad:
 

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Discussion Starter #9
I wired it up tonight, and it works awesome.:ro) Had to finish it with the hoodlamp and a flashlight cause the power went out.Censored
 

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At least you got a hoodlamp on your 2002
Us 2003 owners got Censored for a hoodlamp
 

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Guys, I'm sure that this has been brought up but I really want to do this mod. Do I need to drill a hole some where and connect an on off switch or do you simply connect a wire to two different places like the brake switch to somewhere under the hood?
 

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02 2500HD LB7
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There are several ways you could go about adding a high idle. The way you discussed involves running wire through the firewall and finding power, etc...

The way we have done this involves purchasing a PTO enable switch from GM (~$35 IIRC) which sits in the dash next to the airbag disable switch. It uses existing wiring already in the truck from GM( the connector for the switch is already behind the dash) and only involves splicing 6" of wire from the underhood fuse center to the ECM which is right next to it(why GM never finished the job is beyond me). You can see more of what I am talking about in the link I posted. I didn't rewrite the instructions as to how to hook into the ECM itself as Kennedy already did a great job of showing that in his website.

Basically this way involves only 6" of wire, NO digging around under the dash and running wire through the firewall and finally the best part is you get a lot of funny looks from people when they get in your truck and see a PTO switch on the dash.
 

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Spoolin'It,

Thanks for the link. Has anyone ever found out if this works the same on '03 & '04 LB7s? I'd love to add high idle, & this sure seems like an easier way to do it.
 

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02 2500HD LB7
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The only thing I can tell you about the 2003+ is to pull the dash and see if the connector is there. It should be behind the airbag disable switch( you have to pull that out of the way), on the 01/02's it was taped to the steel brace that runs across the cab behind the dash. It's a rectangualr 8-pin connector IIRC. Let us know what you find.
 

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On my 03 it was there, but it was taped to the air bag disable wires, and the 8 pin connector was covered over with the tape too. After searching behind the dash for a while for the connector I finally saw that it was actually taped to the air bag wires. DOH :eek:
 

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High Idle Question

I purchased the PTO install switch on my '02 LB7 6 SPEED ZF-6, plugged it in, tapped the ECM at the specified location (c-71), and hooked it to 12v power. Works fine, only one problem; as long as c-71 is getting 12v of power the truck only goes about 40 MPH MAX. Remove the fuse and everything back to normal. Any ideas?

PTO switch seems to operate as it should: PTO ON, cruise ON, set activates 1,200 RPM, ACCEL activates 1,700 RPM. Activate brakes idle goes to normal. What gives? PTO switch OFF also does not help. Before the PTO switch install I also tried the brake pedal route (to save a few $) also with the same results.

UI Bulletin #53 says I need to use a Tech II to activate the High idle on the 2500HD (light duty trucks) and does not mention tapping c-71 with the PTO switch installation. I am guessing that with the PTO switch c-71 does not need tapped, but would need activated through a TECH II tool.

Any help appreciated.
 

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wschubbe,

The problem is the wire going to ECM C-71 is only supposed to have power (+) when the truck is idling, once you take it out of park it should NOT have power (+)

If you take that wire and hook it to the brake wire, green with white stripe I believe it will work, with out the PTO switch. When you press on the pedal that wire loses power, and off you go.

If you look at Spoolin'it pictures and info in his link on the previous page you will see where to hook the wire so the PTO switch works normally. But remember you have to turn off the PTO switch when you start moving or it screws up the computer and that's why you can't go over 40mph.

And with the PTO working correctly you won't have to turn the cruise on to get 1,200 rpm, only if you want to go up to 1,700 rpm.

DD
 

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I do not have the automatic, I have a the manual (zf-6) transmission. No green/white wire on mine. I do not believe there is any wire on my brake pedal that has 12 volts running to it unlike the automatic.

Anyone else have the ZF-6 that has this thing working without a seperate switch (from the PTO switch)?
 

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Just put a toggle switch in the + wire to MANUALLY activate/deactivate it...
 

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I was hoping to avoid that, be it looks like that is what I will have to do. I guess I could unhook the PTO switch from the harness and use that as the switch since it is more or less a manual type operation anyway. More wire, but at least I will have a clean look inside the cab.
 
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